Challenge: Braking

OBJECTIVE 1: For a defined driving cycle, calculate the energy required for braking.

A driving cycle is a series of data points represnting the speed of a vehicle vs time.

Energy(E)=1/2*m*v^2

Here mass(m)=1000kg

Here the energy required is maximum up to 281J.

OBJECTIVE 2: Why electric motor can’t develop braking torque at high speed similar to starting? How electric and mechanical brakes are coordinated?

When the motor is at rest and it has to operate at moderate speed high torque is required to bring the motor in operation. At low speed due to less inertia and low RPM high torque can be generated.Whereas when the vehicle is already at high speed the limit is reached by the motor operation and thus any futher higher torque could not be obtained while braking. At high speed the motor will be in the constant power region for both accelerating and braking opearation. But since the peak torque value for deceleration is lower to start with the torque value for the higher speeds is also during braking.

Electric motor, when used in reverse function as generator and will convert mechanical energy into electrical energy. Vehicles propelled by electric motors use them as generators when using regenrative braking.

There are two brake control Strategies:

Series: The Regenerative Braking and the Mechanical Braking both are applied one after another.

Parellel: The Regenerative Braking and the Mechanical Braking both are applied parellely.

OBJECTIVE 3: Make a MATLAB program which plots contour of given motor speed, torque and efficiency values. Attach the code as a .m file attach a screenshot of all the plots

close all
clear all
clc

w=linspace(0,1000);  % speed array
t=linspace(0,300);   % torque array

%loss coefficient
kc=0.2;
ki=0.008;
kw=0.00001;


%meshgrid
[X,Y]=meshgrid(w,t);
copper_loss=(Y.^2)*kc;
iron_loss=X*ki;
windage_loss=(X.^3)*kw
conl=20;

o_p=X.*Y
input_power=copper_loss+iron_loss+windage_loss+o_p+conl;
Eff=(o_p)./(input_power);
n=linspace(0.7,0.95,10);
box off
grid off
contour(X,Y,Eff,n)
title('speed vs Torque')
xlabel('Speed(rad/sec)')
ylabel('Torque(Nm)') 

RESULT: